Orthogonal Processing of Organic Materials Used in Electronic and Electrical Devices

ABSTRACT

An orthogonal process for photolithographic patterning organic structures is disclosed. The disclosed process utilizes fluorinated solvents or supercritical CO 2  as the solvent so that the performance of the organic conductors and semiconductors would not be adversely affected by other aggressive solvent. One disclosed method may also utilize a fluorinated photoresist together with the HFE solvent, but other fluorinated solvents can be used. In one embodiment, the fluorinated photoresist is a resorcinarene, but various fluorinated polymer photoresists and fluorinated molecular glass photoresists can be used as well. For example, a copolymer perfluorodecyl methacrylate (FDMA) and 2-nitrobenzyl methacrylate (NBMA) is a suitable orthogonal fluorinated photoresist for use with fluorinated solvents and supercritical carbon dioxide in a photolithography process. The combination of the fluorinated photoresist and the fluorinated solvent provides a robust, orthogonal process that is yet to be achieved by methods or devices known in the art.

STATEMENT AS TO FEDERALLY SPONSORED RESEARCH

This invention was made with government support under contract 0602821awarded by the National Science Foundation. The government has certainrights in the invention.

BACKGROUND

1. Technical Field

An orthogonal process for patterning organic structures is disclosedwhich utilizes a fluorinated solvent or supercritical CO₂ as a solventfor organic materials. The disclosed process may also utilize afluorinated photoresist in combination with a fluorinated solvent. Thefluorinated photoresist may be a resorcinarene, a copolymer ofperfluorodecyl methacrylate and 2-nitrobenzyl methacrylate, derivativesthereof or other polymer photoresist or molecular glass photoresistshaving sufficient fluorine content. The fluorinated photoresist andfluorinated solvent are used to make patterns of various organicstructures used in electronic (semiconductor) and electrical devices.For example, the materials and techniques disclosed herein may beapplied to the patterning of acidicpoly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), awidely used organic material for which no other straightforwardlithographic patterning method exists.

2. Description of the Related Art

The use of organic materials is becoming widespread in electronic andelectrical device fabrication because organic materials can complementconventional inorganic materials to provide lightweight, inexpensive,and mechanically flexible devices. Advantages of using organic materialslie in the low-temperature, high-throughput fabrication processes forsuch organic materials. The fabrication of a variety of organicelectronic and electrical devices such as organic light emitting diodes(OLEDs), organic thin film transistors (OTFTs), organic solar cells,electrodes and sensors has been demonstrated using spin coating, ink-jetprinting, and other wet printing techniques.

Like traditional inorganic devices, devices made from organic materialsrequire active functional materials to be tailored into micro-patternedand multi-layered device components. Traditional inorganic devices aretypically made using known photolithographic patterning techniques,which provide high-resolution and high-throughput. However, organicsemiconductors and other organic electronics or organic electricalstructures cannot be made using known photolithographic patterningbecause of the chemical incompatibility between the organic materialsand certain patterning agents, specifically, the solvents used duringthe patterning process. The use of conventional organic solventsdeteriorates the performance of the organic materials during thephotoresist deposition and removal. Further, the performance of organicmaterials deteriorates during the pattern development steps usingconventional aqueous base solutions.

To overcome these problems, various strategies have been employed. Onestrategy is to modify the lithographic conditions to accommodate organicmaterials. These efforts include the employment of protective coatingsbetween the active material and photoresist films. Other strategiesinclude attempts to find an “orthogonal solvent,” or a processingsolvent that does not deteriorate the organic layers. Alternativefabrication methods have also been employed including ink-jet printing,shadow mask deposition, vapor deposition through shadow masks, soft andhard imprint lithography, and photolithography. While ink-jet printingboasts continuous roll-to-roll process capabilities and is thepatterning technique of choice for polymeric materials, ink-jet printingresolution is limited to approximately 10-20 μm. Shadow mask depositionis the dominant technique for small molecule patterning, but also hasnotable resolution limitations, typically 25-30 μm at best, althoughspecial masks have shown resolution down to 5 μm. Shadow mask depositionalso requires a high vacuum environment, which can introduce furtherlimitations. Imprint lithography has demonstrated promising results,showing feature resolution down to 10 nm. However, this technique hasonly shown limited applicability with respect to materials and devicearchitectures. Furthermore, all of the aforementioned methods sufferfrom lack of registration, which makes fabrication of multi-layerdevices exceptionally challenging. Multi-layer device architecture isessential for achieving integrated circuits.

To date, no methods for the patterning of organic materials has beenable to provide the resolution and dependability of photolithography. Asa result, photolithography is the most widely-applicable patterningmethod that consistently achieves both high-resolution and registration.Photolithography has the added advantage of being the most developedpatterning technology and the patterning method of choice of thesemiconductor industry.

However, as noted above, there are a limited number of availablesolvents that do not dissolve or adversely damage an organic layerduring a photolithography process. Currently, polar and non-polarsolvents are used to process non-polar and polar active filmsrespectively. For example, one can form a bi-layer structure by using apolar solvent to deposit a polar film on top of a non-polar film.Accordingly, solvent orthogonality can be achieved either by carefullychoosing proper organic material/solvent combinations or by chemicalmodification of organic materials to achieve the desired polarity. Thisstrategy is however problematic because both polar and non-polarsolvents are typically required for photolithographic processes.

Hence, there is a need for an improved approach to the chemicalprocessing of organic materials during the photolithography processes ofan organic electronic device fabrication. Further, there is a need forenvironmentally friendly solvents that are benign to the majority oforganic materials used in organic electronic device fabrication.Finally, there is a need for a robust method for processing organicelectronic devices that avoids damage to the organic material such asdissolution, cracking, delamination or other unfavorable physical orchemical damage.

SUMMARY OF THE DISCLOSURE

Orthogonal processes for patterning of organic structures are disclosed.The disclosed processes may utilize fluorinated solvents orsupercritical CO₂ as an “orthogonal” solvent that does not substantiallyand adversely affect the deposited organic layers. The disclosed processavoids damage to the organic layers during patterning that would becaused by use of conventional solvents.

In a refinement, the disclosed processes may also utilize a fluorinatedphotoresist together with a fluorinated solvent. The fluorinatedphotoresist may be a resorcinarene, a copolymer of perfluorodecylmethacrylate and 2-nitrobenzyl methacrylate, derivatives thereof orother polymer photoresist or molecular glass photoresists havingsufficient fluorine content. The combination of the fluorinatedphotoresist and a fluorinated solvent provides a robust, orthogonalprocess capable of high throughputs.

The fluorinated solvent may be one or more hydrofluoroethers (HFEs) suchas methyl nonafluorobutyl ether, methyl nonafluoroisobutyl ether,isomeric mixtures of methyl nonafluorobutyl ether and methylnonafluoroisobutyl ether, ethyl nonafluorobutyl ether, ethylnonafluoroisobutyl ether, isomeric mixtures of ethyl nonafluorobutylether and ethyl nonafluoroisobutyl ether,3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane,1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane,1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane andcombinations thereof. The fluorinated solvent may also be selected froma broad range of fluorinated solvents, such as chlorofluorocarbons(CFCs): C_(x)Cl_(y)F_(z), hydrochlorofluorocarbons (HCFCs):C_(x)Cl_(y)F_(z)H_(w), hydrofluorocarbons (HFCs): C_(x)F_(y)H_(z),perfluorocarbons (FCs): C_(x)F_(y), hydrofluoroethers (HFEs):C_(x)H_(y)OC_(z)F_(w), perfluoroethers: C_(x)F_(y)OC_(z)F_(w),perfluoroamines: (C_(x)F_(y))₃N, trifluoromethyl (CF₃)-substitutedaromatic solvents: (CF₃)_(x)Ph [benzotrifluoride,bis(trifluoromethyl)benzene], etc.

Improved fluorinated photoresists are also disclosed. The fluorinatedphotoresists include resorcinarene, copolymers of perfluorodecylmethacrylate and 2-nitrobenzyl methacrylate, derivatives thereof, andother polymer photoresist or molecular glass photoresists havingsufficient fluorine content.

Synthetic methods and physical and chemical characterizations ofexemplary resorcinarene photoresists are also disclosed herein. Methodsfor evaluating the lithographic properties of the disclosed fluorinatedphotoresists are also disclosed.

The disclosed methods and photoresists are applicable to organicelectronic devices including, but not limited to various organicsemiconductors, organic light emitting diodes (OLEDs), organic thin filmtransistors (OTFTs), organic solar cells, sensors, etc., and organicelectrical devices including, but not limited to electrodes.

Other advantages and features of the disclosed process will be describedin greater detail below. Although only a limited number of embodimentsare disclosed herein, different variations will be apparent to those ofordinary skill in the art and should be considered within the scope ofthis disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed process, referenceshould be made to the embodiments illustrated in greater detail in theaccompanying drawings, wherein:

FIG. 1 is a schematic illustration of the synthesis procedure for aresorcinarene 5 in accordance with this disclosure;

FIG. 2 is an ¹H NMR spectrum the resorcinarene 5 shown in FIG. 1;

FIG. 3 is a mass spectrum of the resorcinarene 5 (m/z (MALDI-TOF) 2775.4[(M+Na)⁺.C₁₀₀H₆₈F₆₈NaO₁₂ requires M, 2775.35]) shown in FIG. 1;

FIG. 4( a) is a size exclusion chromatogram of the resorcinarene 5 (peaka (M_(n)=5200, D=1.02), peak b (M_(n)=2500, D=1.01), peak c (M_(n)=1700,D=1.01)) shown in FIG. 1;

FIG. 4( b) is an XRD analysis of resorcinarene 5 and its t-Bocderivative 6 shown in FIG. 1;

FIG. 5 is an ¹H NMR spectrum of t-Boc protected R_(F)-resorcinarene 6shown in FIG. 1;

FIG. 6 is an IR spectrum of t-Boc protected R_(F)-resorcinarene 6 shownin FIG. 1;

FIG. 7 is a DSC thermogram of t-Boc protected R_(F)-resorcinarene 6shown in FIG. 1;

FIG. 8 is a TGA thermogram of t-Boc protected R_(F)-resorcinarene 6shown in FIG. 1;

FIG. 9 illustrate the chemical structures of HFEs used in accordancewith this disclosure;

FIG. 10 is a contrast curve under UV (λ=365 nm) exposure conditions forthe resorcinarene 6 (FIG. 1) in combination with a photo acid generator(PAG) (5% w/w over 6) on a Si wafer:

FIG. 11 illustrates a fluorescent microscope image of overlaid patterns(feature widths are 20, 10, 5 and 2 μm) of poly(9,9-dioctylfluorene)(top) and [Ru(bpy)₃]²⁺ (PF₆ ⁻)₂ (bottom) in accordance with thisdisclosure;

FIG. 12( a) illustrates the structure of a PAG used in the lithographicevaluation in accordance with this disclosure;

FIG. 12( b) is an SEM image of the resorcinarene 6 (FIG. 1) on a glasswafer (scale bars are 10 μm) in accordance with this disclosure;

FIG. 12( c) is an optical microscope image of the resorcinarene 6(FIG. 1) on a polyimide-coated wafer (scale bars are 10 μm) inaccordance with this disclosure;

FIG. 12( d) is an SEM image of the resorcinarene 6 (FIG. 1) on a Siwafer under e-beam exposure conditions (100 nm and 80 nm patterns) inaccordance with this disclosure;

FIG. 13( a) schematically illustrates a procedure for the lift-offpatterning of functional materials in accordance with this disclosure;

FIG. 13( b) is an optical microscope image of a patterned P3HT inaccordance with this disclosure;

FIG. 13( c) is a fluorescent microscope image of overlaid patterns(feature width 5 μm) of poly(9,9-dioctylfluorene) (top) and [Ru(bpy)₃]²⁺(PF₆ ⁻)₂ (bottom) in accordance with this disclosure;

FIG. 14( a) illustrates the chemical structures of a disclosed HFEsolvents including a mixture of two isomers, with a boiling point of 61°C.;

FIG. 14( b) illustrates the chemical structure of another disclosed HFEsolvent with a boiling point of 130° C.;

FIG. 15( a) graphically illustrates P3HT OTFT gate sweep curves taken ata source-drain voltage of −100V before and after solvent treatment;

FIG. 15( b) graphically illustrates a temporal response of emission of[Ru(bpy)₃]²⁺ (PF₆ ⁻)₂ electroluminescent devices at 3V applied biasbefore and after solvent treatment; and

FIG. 15( c) is a photograph of a [Ru(bpy)₃]²⁺ (PF₆ ⁻)₂electroluminescent device operating in HFE illustrated in FIG. 14( a)under boiling conditions;

FIG. 16( a) schematically illustrates a disclosed HFE-based lift-offpatterning technique for organic materials;

FIG. 16( b) schematically illustrates a disclosed imaging process of thephotoresist employed in the HFE-based patterning illustrated in FIG. 16(a);

FIG. 16( c) is an optical micrograph of a patterned [Ru(bpy)₃]²⁺ (PF₆⁻)₂ film;

FIG. 17 illustrates alternative fluorinated photoresists to theresorcinarene illustrated in FIG. 1;

FIG. 18 illustrates the synthesis of the fluorinated photoresistillustrated in FIG. 17;

FIGS. 19( a)-19(d) are four patterned photoresist images of polymer 10of FIG. 18 using HFE-7600 is a solvent and patterned under 248 and 365nm exposure conditions including (a) at 365 nm on Si, (b) at 365 nm onglass, (c) at 365 nm on PEDOT:PSS film, and (d) e-beam exposure on Si;

FIGS. 20( a)-20(f) illustrate a photolithography process ofPEDOT:PSS/pentacene bottom-contact OTFT including (a) a schematicillustration of device fabrication, (b) an AFM image of a 5 μm(width)×50 μm (length) pentacene channel between PEDOT:PSS electrodes,(c) another AFM image of a 5 μm (width)×50 μm (length) pentacene channelbetween PEDOT:PSS electrodes, (d) an optical image of OTFT, (e) a deviceperformance plot and (f) another device performance plot;

FIG. 21 is a contrast curve at 248 nm for polymer 10 of FIG. 18;

FIG. 22 is another contrast curve at 365 nm for polymer 10 of FIG. 18;

FIG. 23 is a differential scanning calorimetry (DSC) curve of polymer 10of FIG. 18;

FIG. 24 is a thermogravimetric analysis (TGA) curve for polymer 10 ofFIG. 18;

FIG. 25 is a gel permeation chromatography (GPC) curve for polymer 10 ofFIG. 18;

FIG. 26 is a nuclear magnetic resonance (¹H NMR) spectrum for polymer 10of FIG. 18;

FIG. 27 is an infrared (IR) spectrum for polymer 10 of FIG. 18;

FIG. 28 presents two optical microscopic images of patterned PEDOT:PSSon a Si wafer; and

FIG. 29 illustrates a photolithography process utilizing supercriticalcarbon dioxide is a solvent as an alternative to the use of afluorinated solvent.

In certain instances, details which are not necessary for anunderstanding of the disclosed processes or materials or which renderother details difficult to perceive may have been omitted. It should beunderstood, of course, that this disclosure is not limited to theparticular embodiments illustrated herein.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

The term chemical processing as used herein shall mean any chemicaltreatment such as cleaning, depositing a second layer from solution toform multilayer devices, and depositing/developing resist layers forphotolithographic patterning.

Fluorous Solvents

Fluorous solvents are perfluorinated or highly fluorinated liquids,which are typically immiscible with organic solvents and water. Amongthose solvents, segregated hydrofluoroethers (HFEs) are well known to behighly environmentally friendly, “green” solvents. HFEs arenon-flammable, have zero ozone-depletion potential, low global warmingpotential and show very low toxicity to humans. HFEs were introduced toindustry in 1994 as third generation hydrofluorocarbon liquids to beused as replacement of chlorofluorocarbons and hydrochlorofluorocarbonrefrigerants. HFEs have also been demonstrated as environmental friendlycleaning solvents for electronics. Nevertheless, the use of HFEs in theprocessing of organic electronics and electrical structures is yet to bereported.

One or more hydrofluoroethers (HFEs) may be used, such as methylnonafluorobutyl ether, methyl nonafluoroisobutyl ether, isomericmixtures of methyl nonafluorobutyl ether and methyl nonafluoroisobutylether, ethyl nonafluorobutyl ether, ethyl nonafluoroisobutyl ether,isomeric mixtures of ethyl nonafluorobutyl ether and ethylnonafluoroisobutyl ether,3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-decafluoro-2-trifluoromethyl-hexane,1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-trifluoromethyl-pentane,1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane andcombinations thereof.

Readily available HFEs include isomeric mixtures of HFEs including, butnot limited to methyl nonafluorobutyl ether and methylnonafluoroisobutyl ether (HFE 7100; FIGS. 9 and 14( a)), ethylnonafluorobutyl ether and ethyl nonafluoroisobutyl ether (HFE-7200; FIG.9),3-ethoxy-1,1,1,2,3,4,4,5,5,6,6,6-dodecafluoro-2-trifluoromethyl-hexane(HFE 7500; FIGS. 9 and 14( b)) and1,1,1,2,3,3-hexafluoro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-pentane (HFE7600; FIG. 9).

The fluorinated solvent may also be selected from a broad range offluorinated solvents, such as chlorofluorocarbons (CFCs):C_(x)Cl_(y)F_(z), hydrochlorofluorocarbons (HCFCs):C_(x)Cl_(y)F_(z)H_(w), hydrofluorocarbons (HFCs): C_(x)F_(y)H_(z),perfluorocarbons (FCs): C_(x)F_(y), hydrofluoroethers (HFEs):C_(x)H_(y)OC_(z)F_(w), perfluoroethers: C_(x)F_(y)OC_(z)F_(w),perfluoroamines: (C_(x)F_(y))3N, trifluoromethyl (CF₃)-substitutedaromatic solvents: (CF₃)_(x)Ph [benzotrifluoride,bis(trifluoromethyl)benzene], etc.

Resorcinarenes

The synthesis and evaluation of a semi-perfluoroalkyl resorcinarene,which is capable of being processed in fluorinated solvents, isdescribed herein. This novel, high-performance imaging material isspecifically designed to be orthogonal to the vast majority of organicelectronic and electrical structures and hence enable theirphotolithographic patterning. Furthermore, this material paves the wayfor the multilevel patterning of organic structures, as demonstrated bythe fabrication of overlaid patterns of a polyfluorene and a transitionmetal complex.

In general, materials with higher fluorine content dissolve better influorous solvents. On the other hand, those materials are less adhesiveon non-fluorinated surfaces. Therefore, a material with a limited degreeof fluorination while still exhibiting sufficient solubility and uniformdissolution behavior in fluorinated solvents was needed. Applicants havefound that resorcinarene materials show excellent patterning propertiesunder conventional lithographic conditions. The same molecular frameworkwas adapted, to which four semi-perfluoroalkyl chains and eightacid-cleavable tert-butoxycarbonyl (t-Boc) groups were appended. Theresulting resorcinarene 6 in FIG. 1 had 36% fluorine content by weight.Resorcinarene 6 is able to form a negative tone image by transformationinto an insoluble form upon an acid-catalyzed deprotection reaction, inwhich H+ is liberated from the photoacid generator (PAG) under UVexposure (FIG. 1).

As illustrated in FIG. 1, synthesis of the resorcinarene 6 can beginwith the alkylation of 4-hydroxybenzaldehyde 1 with thesemi-perfluroalkyl iodide 2. The recrystallized product 3 was thenreacted with an equimolar amount of resorcinol under acidic conditions.The resorcinarene 5, which is only sparingly soluble in THF, wasrecovered as a fine, pale-yellow powder in high yield. Size exclusionchromatography showed that the product 5 is composed mainly of twocompounds, one with a number average molecular weight (Mn) of about 2500and the other with a Mn of about 1700 compared to the polystyrenestandard. Without being bound by any particular theory, it is believedthat those two are stereo-isomers which have different hydrodynamicvolumes. The presence of stereo-isomers may stabilize the amorphousstate of the resorcinarene 6, which would enable quality film formation.t-Boc protection of the eight hydroxyl groups in the resorcinarene 5 iscompleted in a mixed solvent of THF and benzotrifluoride.Thermogravimetric analysis (TGA) and differential scanning calorimetry(DSC) shows that resorcinarene 6 is thermally stable up to 150° C. andundergoes glass transition at 82° C. Solubility tests confirmed thatresorcinarene 6 is moderately soluble in HFE-7200 (FIG. 9).

Photo-Acid Generators

Lithographic evaluation began with spin-coating films of theresorcinarene 6 and PAG mixture on various substrates. The PAG 7illustrated in FIG. 12( a) isN-nonafluorobutane-sulfonyloxy-1,8-naphthalimide (orN-hydroxynaphthalimide perfluorobutylsulfonate) and was employed becauseof its good sensitivity under UV (λ=365 nm) exposure conditions. Othersuitable PAGs may includeN-nonafluoropropane-sulfonyloxy-1,8-naphthalimide,N-nonafluoroethane-sulfonyloxy-1,8-naphthalimide,N-nonafluoromethane-sulfonyloxy-1,8-naphthalimide.

Still other PAGs include triarylsulfonium perfluroalkanesulfonates suchas triphenylsulfonium perfluorooctanesulfonate, triphenylsulfoniumperfluorobutanesulfonate and triphenylsulfoniumtrifluoromethanesulfonate:

Triarylsulfonium hexafluorophosphates (or hexafluoroantimonates) such astriphenylsulfonium hexafluorophosphate and triphenylsulfoniumhexafluoroantimonate may be used as PAGs:

Triaryliodonium perfluroalkanesulfonates such as diphenyliodoniumperfluorooctanesulfonate, diphenyliodonium perfluorobutanesulfonate,diphenyliodonium trifluoromethanesulfonate,di-(4-tert-butyl)phenyliodonium, perfluorooctanesulfonate,di-(4-tert-butyl)phenyliodonium perfluorobutanesulfonate, anddi-(4-tert-butyl)phenyliodonium trifluoromethanesulfonate may also beused a PAGs:

Triaryliodonium hexafluorophosphates (or hexafluoroantimonates) such asdiphenyliodonium hexafluorophosphate, diphenyliodoniumhexafluoroantimonate, di-(4-tert-butyl)phenyliodoniumhexafluorophosphate, and di-(4-tert-butyl)phenyliodoniumhexafluoroantimonate may be used as PAGs:

Norbornene-based non-ionic PAGs such asn-hydroxy-5-norbornene-2,3-dicarboximide perfluorooctanesulfonate,n-hydroxy-5-norbornene-2,3-dicarboximide perfluorobutanesulfonate, andn-hydroxy-5-norbornene-2,3-dicarboximide trifluoromethanesulfonate maybe used:

Naphthalene-based non-ionic PAGs such as n-hydroxynaphthalimideperfluorooctanesulfonate, n-hydroxynaphthalimideperfluorobutanesulfonate and n-hydroxynaphthalimidetrifluorometahnesulfonate may also be used:

Suitable PAGs are not limited to those specifically mentioned above.Combinations of two or more PAGs may be used as well, which may or maynot include PAG 7.

Further, while the examples disclosed herein utilize UV radiation,electron beam and other forms of radiation are possible and consideredwithin the scope of this disclosure.

Uniform films were cast on Si, glass and polyimide-coated wafers from asolution in HFE-7500 (4 parts by vol.) mixed with a small amount ofpropylene glycol methyl ether acetate (1 part by vol.). Following UVexposure (84 mJ cm-2 with Si substrate), baking (at 70° C.) anddevelopment in HFE-7200, at least 600 nm features were generated on theaforementioned substrates, as illustrated in FIGS. 12( b) and 12(c). Asillustrated in FIG. 12( d), under electron-beam exposure conditions, 80nm patterns could be achieved without extensive optimization, whichdemonstrates that lithography employing fluorinated solvents can be auseful tool to realize sub 100 nm features.

The new imaging material and lithographic processing in fluorinatedsolvents can be applied to fabricating micron-sized patterns of organicelectronic materials. FIG. 13( a) illustrates a procedure for lift-offpatterning. A developed resorcinarene image becomes soluble again influorinated solvents through treatment with a solubilizing agent such asa silazane. One suitable solubilizing agent is hexamethyldisilazane(HMDS; 1,1,1,3,3,3-hexamethyldisilazane), which reprotects the phenolichydroxyl residue with trimethylsilyl (TMS) group. Other solubilizingagents include heptamethyldisilazane, 1,1,3,3-tetramethyldisilazane andcombinations thereof with or without HMDS. Deposition of an organicmaterial and following lift-off of the resorcinarene film in hotHFE-7100 generate an organic material pattern. It is demonstrated thatpoly(3-hexylthiophene) (P3HT) (FIG. 13( b)),poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) andAu could be patterned down to 5 μm size. As a step further, an overlaidmaterials pattern was fabricated to demonstrate, for the first time, themultilevel patterning of solution capable of processing organic layers.The electroluminescent material poly(9,9-dioctylfluorene) was patternedfirst according to the scheme in FIG. 2, and then the same procedure wasrepeated with tris(2,2′-bipyridine)ruthenium(II)bis(hexafluorophosphate)[Ru(bpy)3]2+(PF6-)2 on top of the patterned poly(9,9-dioctylfluorene)film. As illustrated in FIG. 13( c), overlaid features down to 5 μm sizewere made successfully. The results show that the new imaging materialdescribed here brings unique capabilities to the world of organicelectronics.

Experimental (Resorcinarene; FIGS. 1-16)

Materials and solvents: Resorcinol, benzotrifluoride (anhydrous) andpropylene glycol monomethyl ether acetate (PGMEA) were purchased fromSigma-Aldrich and used as received. Di-tert-butyl dicarbonate[(t-Boc)₂O] was purchased from Fluka (Sigma-Aldrich).4-Hydroxybenzaldehyde was purchased from Alfa Aesar. Anhydrous Et₂O,THF, DMF and EtOH were purchased and used without further drying. 3M™Novec™ Engineered Fluid HFE-7100, 7200, 7300 and 7500 were provided by3M. 1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8-Heptadecafluoro-12-iodododecane 2,and N-nonafluorobutane-sulfonyloxy-1,8-naphthalimide 7 (FIG. 12( a))were prepared according to the modified literature methods.

Characterization (FIGS. 1-16)

¹H NMR spectra were recorded on a Varian Inova-400 (400 MHz) orInova-500 (500 MHz) spectrometer at ambient temperature, using thechemical shift of a residual protic solvent (CHCl₃ at δ 7.28 ppm,acetone at 2.05 ppm, or DMSO at δ 2.50 ppm) as an internal reference.All chemical shifts are quoted in parts per million (ppm) relative tothe internal reference and coupling constants J are measured in Hz. Themultiplicity of the signal is indicated as follows: s (singlet), d(doublet), t (triplet), q (quartet), m (multiplet), dd (doublet ofdoublets), dt (doublet of triplets), dm (doublet of multiplets) and br s(broad singlet). ¹³C NMR spectra were recorded on a Varian Inova-400(100 MHz) or Inova-500 (125 MHz) spectrometer using the centralresonance of the triplet of CDCl₃ at δ 77.0 ppm Infrared absorptionswere measured for samples in a KBr pellet or on a NaCl window with aMattson Instruments Galaxy 2020 spectrophotometer. Microanalyses werecarried out by Quantitative Technologies, Inc. Mass spectrometry wasperformed by the Department of Molecular Biology and Genetics, CornellUniversity. Thermo gravimetric analysis (TGA) was performed on a TAinstruments Q500 at a heating rate of 10° C. min⁻¹ under N₂. The glasstransition temperature (T_(g)) of a resist material was measured on a TAInstruments Q1000 modulated differential scanning calorimeter (DSC) at aheat/cool rate of 10° C. min⁻¹ under N₂ for heat/cool/heat cycles.Powder X-ray diffraction (PXRD) patterns were obtained using a ScintagTheta-Theta XDS2000 diffractometer to examine the crystallinity of thebulk material. Size exclusion chromatography was performed on a WatersGPC system (Waters 486 UV detector) by eluting THF (1 cm³ min⁻¹) at 40°C.

Synthesis of Resorcinarene Photoresist Materials (FIGS. 1-16)

4-(5,5,6,6,7,7,8,8,9,9,10,10,11,11,12,12,12-Heptadecafluorododecyloxy)benzaldehyde 3 (FIG. 1)

To a magnetically stirred solution of 2 (prepared by a modifiedliterature procedure) (8.00 g, 13.3 mmol) and 4-hydroxybenzaldehyde(1.95 g, 15 9 mmol) in DMF (30 cm³) was added K₂CO₃ (3.67 g, 26.6 mmol).The suspension was then heated to 70° C. After the solution was stirredfor 2 h, the reaction was allowed to cool to ambient temperature andquenched by the addition of water (150 cm³). The product was extractedwith Et₂O (200 cm³). The organic layer was washed with 1 M NaOH aqueoussolution (100 cm³), brine (100 cm³), dried over anhydrous MgSO₄ andconcentrated under reduced pressure. The crude product was purified bycrystallization from MeOH (80 cm³) to give the aldehyde 3 as colorlesscrystals (6.12 g, 80%); mp 50-51° C. (MeOH); (Found: C, 38.2; H, 2.1.C₁₉H₁₃F₁₇O₂ requires C, 38.3; H, 2.2%); IR (KBr) ν_(max): 2955, 2887,1687, 1601, 1515, 1311, 1257, 1217, 1153, 1042, 1013, 956, 841, 659cm⁻¹; 1H NMR (500 MHz, CDCl₃): δ=1.82-1.88 (m, 2H, CF₂CH₂CH₂), 1.91-1.97(m, 2H, CH₂CH₂O), 2.19 (ddd, J=8, 18, 27 Hz, 2H, CF₂CH₂), 4.10 (t, J=6Hz, 2H, CH₂O), 7.00 (d, J=8.5 Hz, 2H, Ar—H), 7.85 (d, J=8.5 Hz, 2 H,Ar—H), 9.90 ppm (s, 1H, Ar—CHO); ¹³C NMR (125 MHz, CDCl₃): δ=17.5, 28.8,30.9, 67.8, 114.9, 130.3, 132.3, 164.1, 191.0 ppm; m/z (MALDI) 597.11[(M+H)⁺. C₁₉H₁₄F₁₇O₂: requires M, 597.07].

Semi-perfluorododecylated resorcinarene 5 (FIG. 1)

To a magnetically stirred solution of 3 (7.00 g, 11.7 mmol) andresorcinol (1.29 g, 11.7 mmol) in anhydrous EtOH (50 cm³) was addedconcentrated HCl aqueous solution (2.3 cm³) at 75° C. Just after theaddition of HCl, the color of the reaction mixture changed to red withprecipitation of solid particles. After the suspension was stirred for 2h at 75° C., it was cooled to ambient temperature and filtered withwashing with EtOH. The recovered solid was dispersed in EtOH (100 cm³),stirred for 10 min and filtered again with washing with EtOH. The solidwas then dried under reduced pressure at 50° C. to give theR_(F)-resorcinarene 5 as a pale-yellow powder (7.55 g); (Found: C, 42.7;H, 2.4. C₁₀₀H₆₈F₆₈O₁₂ requires C, 43.6; H, 2.5%); IR (KBr) ν_(max):3400, 2953, 2927, 1617, 1512, 1246, 1206, 1153, 1079, 967, 829, 725, 708cm⁻¹; ¹H NMR (400 MHz, acetone-d₆): δ=1.77-2.00 (m, 16H,4×CH₂CH₂CH₂CF₂), 2.23-2.43 (m, 8H, 4×CH₂CF₂), 3.88-4.16 (8H, 4×OCH₂),5.67-5.89 (4H, 4×Ar₃CH), 6.18-6.80 (m, 24H, Ar—H), 7.20-7.58 ppm (8H,8×Ar—OH); m/z (MALDI) 2775.4 [(M+Na)⁺. C₁₀₀H₆₈F₆₈NaO₁₂ requires M,2775.35].

The ¹H NMR spectrum and mass spectrum of R_(F)-resorcinarene 5 areillustrated in FIGS. 2 and 3, respectively; the size exclusionchromatogram of the resorcinarene 5 (peak a (Mn=5200, D=1.02), peak b(M_(n)=2500, D=1.01), peak c (M_(n)=1700, D=1.01)) is illustrated inFIG. 4( a); and the XRD analysis of resorcinarene 5 and its t-Bocderivative 6 is illustrated in FIG. 4( b).

t-Boc protection of the semi-perfluorododecylated resorcinarene 6

To a magnetically stirred solution of 5 (6.12 g, 2.22 mmol, partlysoluble in THF) and 4-(dimethylamino)pyridine (0.271 g, 2.22 mmol) inTHF (65 cm³) was added a solution of (t-Boc)₂O (4.85 g, 22.2 mmol) inTHF (15 cm³) at ambient temperature. After the solution was stirred for1 h, benzotrifluoride (120 cm³) was added to it. The solution wasstirred overnight and then washed with water (100 cm³) three times. Theorganic layer was dried over anhydrous MgSO₄, passed through a shortplug of silica gel with washing with benzotrifluoride and concentratedunder reduced pressure. The concentrated solution was added to MeOH (500cm³) drop-wise. The precipitated powder was filtered and dried underreduced pressure to give t-Boc protected R_(F)-resorcinarene 6 as anoff-white powder (6.64 g, 84%); (Found: C, 46.7; H, 3.7. C₁₄₀H₁₃₂F₆₈O₂₈requires C, 47.3; H, 3.7%); Tg (DSC) 82° C.; dec. temp. (TGA) 156° C.(3% wt loss); IR (KBr) ν_(max): 2985, 2939, 2882, 1765, 1614, 1514,1374, 1248, 1211, 1145, 1097, 1042, 854, 779, 723, 705, 654 cm⁻¹; ¹H NMR(500 MHz, CDCl₃+CFCl₃): δ=1.25-1.47 [72 H, 8×(CH₃)₃C], 1.79-1.96 (m, 16H, 4×CH₂CH₂CH₂CF₂), 2.08-2.25 (m, 8H, 4×CH₂CF₂), 3.85-4.04 (8H, 4×OCH₂),5.63-5.75 (4H, 4×Ar₃CH), 6.15-7.13 ppm (m, 24H, Ar—H).

The ¹H NMR spectrum and IR spectrum of t-Boc protectedR_(F)-resorcinarene 6 are illustrated in FIGS. 5 and 6, respectively;and the DSC and TGA thermograms of t-Boc protected R_(F)-resorcinarene 6are illustrated in FIGS. 7 and 8, respectively.

Lithographic Evaluation (FIGS. 1-16)

The lithographic properties of t-Boc protected R_(F)-resorcinarene 6using three different substrates (Si wafer, double polished glass waferand polyimide-coated Si wafer) were investigated using a GCA Autostep200 DSW i-line Wafer Stepper. In the case of polyimide coating, thickfilm of Photoneece® PWDC-1000 (Toray) was used on a 4″ Si wafer. Theresulting precursor film was then baked according to the heating/coolingprogram up to 350° C.

The resorcinarene films were spin-coated from a 10% (w/v) solution in amixture of HFE-7500 (1.6 cm³) and PGMEA (0.4 cm³) containing 5% (w/w,with respect to the resist 6/PAG 7, prepared by a modified literatureprocedure). The spin-coating was performed at 2000 rpm (acceleration:400 rpm s⁻¹) followed by post apply bake (PAB) at 70° C. for 60 seconds.The resulting film had a thickness of about 360 nm. The adequateexposure dose varied with the substrate. F the Si wafer, the dose was 84mJ cm⁻²; for the glass wafer, the dose was 120 mJ cm⁻²; and, asillustrated in FIG. 10, the dose was 72 mJ cm⁻² for the polyimide-coatedwafer.

After exposure the film was baked (post exposure bake, PEB) at 70° C.for 30 s, developed in HFE-7200 for 20 s and rinsed with HFE-7300. Thethickness of the film after exposure was 265 nm due to the loss of t-Bocgroup upon deprotection reaction.

Additional Polymer Photoresists (P(FDMA-NBMA); FIGS. 17-28)

As indicated in FIGS. 17-18, other polymer photoresists and molecularglass photoresists which have an appropriate fluorine content areapplicable to the techniques disclosed herein. For example, thephotoresist material illustrated in FIGS. 17-18 works under identicalconditions set forth above for the resorcinarene resist 5 of FIG. 1. Thephotoresist material is a copolymer of perfluorodecyl methacrylate and2-nitrobenzyl methacrylate (P(FDMA-NBMA)) which has a light-sensitivecomponent also showed a similar patterning capability to theresorcinarene resist 5. FIGS. 17-18 shows the structure of the copolymerP(FDMA-NBMA) and summarizes the general process scheme.

Referring to FIG. 18, the copolymer 10 is derived from the highlyfluorinated perfluorodecyl methacrylate monomer 7 and the photo-labile2-nitrobenzyl methacrylate monomer 8 was expected to yield a copolymermaterial which exhibits a solubility switch following UV irradiation.The photo-labile component, the ester of 2-nitrobenzyl alcohol andmethacrylic acid, decomposes under UV exposure to yield a carboxylicacid and nitrosobenzaldehyde 11. The resulting polymer 12 is no longersoluble in a fluorinated solvent. Following development in a fluorinatedsolvent, the still-soluble unexposed regions are washed away to leavethe insoluble exposed area as a negative-tone image.

The two monomers (7 and 8) were randomly copolymerized by radicalinitiation with 2,2′-azobis(2-methylpropionitrile) (AIBN). Multiplepolymers were synthesized with varying compositions; polymers whichlacked sufficient incorporation of the fluorinated monomer provedinsoluble in a fluorinated solvent. Conversely, polymers withoutsufficient incorporation of the photosensitive monomer provedunpatternable. Percent compositions of the two monomers were varied toobtain optimum photosensitivity while still retaining enoughfluorination to be processable in fluorinated solvents.

To demonstrate patterning properties, the polymer 10 waslithographically evaluated on both Si and glass substrates. Photoresistwas spin-coated from HFE-7600 and then patterned under 248 and 365 nmexposure conditions. Pattern development was carried out in HFE-7200.FIG. 19 shows well-resolved sub-micron lines on Si and glass. It isnotable that this photoresist is soluble in a fluorinated solvent,without a co-solvent, and that all processing steps are achieved throughfluorinated solvents.

Sensitivity profiles were obtained for polymer 10 at both 248 and 365nm. The polymer exhibits very different sensitivities at differentwavelengths. At 248 nm, the dose is 84 mJ cm-2 whereas at 365 nm, thedose is 2700 mJ cm-2. However, this behavior is expected as thenitrobenzyl group is likely to undergo faster decomposition by theirradiation of high energy photons.

To further explore the patterning properties, the photoresist was alsopatterned under electron-beam (e-beam) exposure conditions.Well-resolved lines down to 100 nm were obtained, shown in FIG. 19( d).

It should be emphasized that the photosensitive monomer 9 was carefullyselected to enable non-chemically amplified patterning; an imagingmechanism which does not rely on acid-catalyzed deprotection reactions.The advantages of this pathway are substantial, in particular, for thepatterning of PEDOT:PSS films. PEDOT:PSS is a difficult material topattern with acid-sensitive photoresists (i.e. photoresists requiring aphotoacid generator) in that PEDOT:PSS itself, being highly acidic, candecompose the resist. Typically, following patterning with a chemicallyamplified resist, a thin layer (ca. 10-20 nm) of decomposed photoresistis left on the PEDOT:PSS interface.

Preliminary studies in PEDOT:PSS patterning were first carried out withour acid-stable photoresist. PEDOT:PSS was spin-coated onto an Si waferin a thin film. The polymer 10 was then applied and subsequentlyremoved. Before and after measurements showed the thickness of thePEDOT:PSS film to remain exactly the same, indicating no resistdecomposition. Similarly, PEDOT:PSS was again spun-cast, followed byphotoresist application. The photoresist was then flood-exposed with 248nm UV light and subsequently removed. Before and after thicknessmeasurements again show the PEDOT:PSS film unchanged. Therefore, noresidual layers of decomposed resist were found, as withchemically-amplified resists. The PEDOT:PSS interface is left clean andunaffected following resist removal.

Two sets of ITO/PEDOT:PSS/Metal devices were fabricated and tested, onewith PH 500 and one with AI4083 (PH500 and AI4083 commercially-availablefrom H. C. Starck). A layer of photoresist was deposited onto thePEDOT:PSS films, flood-exposed with UV light and then removed. Referencedevices were fabricated with pristine PEDOT:PSS films. Both sets of testdevices showed essentially the same resistance and I-V curves as thereference devices, indicating that our photoresist has no detrimentaleffects on device performance These results collectively support ournon-chemically amplified photoresist as an ideal material for PEDOT:PSSpatterning.

The actual patterning of PEDOT:PSS film was then demonstrated.Photoresist films were spun-cast onto films of PEDOT:PSS and thenpatterned at 365 nm, shown in FIG. 19. Pattern resolution was consistentwith that of the photoresist patterned on Si alone. Patterns weretransferred to PEDOT:PSS via oxygen-plasma etching and the photoresistwas subsequently removed. PEDOT:PSS patterns with sub-micron resolutionwere obtained.

To demonstrate the potential of this resist, we fabricated simplebottom-contact organic thin film transistors (OTFTs) with patternedpentacene film on top of patterned PEDOT:PSS source and drainelectrodes. The optical image and atomic force microscopy (AFM) imagesof a typical 5 μm channel length OTFT device are shown in FIG. 20. FIG.20( b) shows that the pentacene fully covers both the transistor channeland the PEDOT:PSS contacts, without any observable delaminationoccurring after lift-off in HFE. FIG. 20( c) shows that larger grains(˜0.5 μm) are formed inside the channel, with a mean roughness of 40 nm.Pentacene attempts to grow into islands (˜80 nm height) on the PEDOT:PSScontacts.

Transistor performance was evaluated in a high vacuum probe station.OTFTs with channel lengths of 5, 10, 20, and 50 microns were fabricatedand tested. The typical electrical characteristics of a fabricated 5 μmchannel length OTFT are shown in FIGS. 20( e)-20(f). The field effectmobility in the saturation regime was extracted from the transfercharacteristics using the following equation:

${I_{{DS},{saturation}} = {\frac{W}{2L} \cdot \mu_{sat} \cdot C_{r} \cdot \left( {V_{G} - V_{TH}} \right)^{2}}},$

where IDS is the drain current, Cr is the capacitance per unit area ofthe gate dielectric layer, VG is the gate voltage, VTH is the thresholdvoltage. VTH was determined from the intercept in the plot of (IDS)1/2vs. VG. For the presented device, the value of 0.029 cm2 V-1s-1 wasobtained for the charge carrier mobility in the saturation regime. Theon-off current ratio was found to be more than 104. For all fabricateddevices, the channel length to channel width ratio was kept thesame—therefore all other devices show similar performance. The obtainedvalues for carrier mobility are higher or comparable to previouslyreported values for Pentacene channel, PEDOT:PSS electrodes OTFTsobtained by other patterning techniques.

Thus, non-chemically amplified resists for patterning organic electronicmaterials are disclosed that provide sub-micron patterning capabilitiesat 248 nm and 365 nm conditions and have shown 100 nm resolution undere-beam exposure. Sub-micron patterning of PEDOT:PSS is also disclosed, amaterial for which the disclosed photoresists are particularly suitable.A bottom-contact transistor patterned with the disclosed photoresistsexhibits comparable or better performance than previously reportedbottom-contact transistors of the same type obtained by other patterningtechniques.

Experimental (FIGS. 17-28)

Materials: 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-Heptadecafluorodecylmethacrylate 1 and benzotrifluoride were purchased from Sigma-Aldrichand used as received. 2,2′-azobis(2-methylpropionitrile) wasrecrystallized from CHCl₃. 3M™ Novec™ Engineered Fluid HFE-7100, 7200,and 7600 were donated from 3M USA. PEDOT:PSS was purchased from H. C.Starck and used as received. Pentacene was purchased from Kintec andused as received.

Synthesis of the polymer photoresist 10: 2-Nitrobenzyl methacrylate 9was prepared and purified by recrystallization from CH2Cl2-hexanes mixedsolvent after column chromatography (1.05 g, 4.75 mmol) and3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10-heptadecafluorodecyl methacrylate(5.95 g, 11.2 mmol) were added to a 25 cm3 schlenk tube.Benzotrifluoride (7 cm3) and 2,2′-azobis(2-methylpropionitrile) (AIBN,0.07 g, 0.43 mmol) were then added to the mixture. The tube was sealedthen degassed by three freeze-thaw cycles in liquid N₂ under reducedpressure. The solution was magnetically stirred at 72° C. for 12 hoursunder a N₂ atmosphere. The solution was precipitated in hexanes thendried under reduced pressure to give a colorless solid 3 (5.5 g); IR(KBr): ν=3002, 1737, 1537, 1480, 1348, 1211, 1151, 971, 788, 734, 705,654 cm-1; 1H NMR [400 MHz, CDCl3 (1 part by vol.)+CFCl₃ (1 part byvol.), δ] 8.05 (br s, 1H, Ar—H), 7.67 (br s, 2H, Ar—H), 7.52 (br s, 1H,Ar—H), 5.39 (br s, 2H, ArCH2O), 4.26 (br s, 6H, CH2CF2), 2.50 (br s, 6H,CH2CH2CF2), 2.21-0.66 ppm (m, 20H); Mn=17,000, Mw/Mn=2.4.

The lithographic properties of the polymer 10 were investigated usingtwo different substrates (Si and glass wafer) were investigated using aGCA Autostep 200 DSW i-line Wafer Stepper. The resist films werespin-coated from a resist (0.15 g) solution in HFE-7600 (1.5 g) at 2000rpm followed by post-apply bake at 110° C. The resulting film had athickness of ca. 460 nm After UV exposure, the film was baked at 110° C.for 60 seconds, developed in HFE-7200 for 40 seconds.

Bottom-contact transistors were fabricated as follows. A thin film ofPEDOT:PSS (Clevios PH500, H.C. Stark) was spin-coated onto a Si waferwith 360 nm of thermally grown oxide and baked at 180° C. for 10minutes. A layer of the polymer 10 was spin-coated onto the PEDOT:PSSfilm. The resist film was patterned in HFE-7200 and the remaining imagewas then transferred onto the PEDOT:PSS film via O₂-plasma etch. Theresist film was then washed away in a 2-propanol (10% by vol.) HFE-7100mixture. Onto this patterned PEDOT:PSS film was spin-coated anotherlayer of the resist 10 which was also photo-patterned. A thin film (ca.20 nm) of pentacene was thermally evaporated (substrate temperature −50°C., residue gas pressure <5×10-7 Torr, at a rate of 0.05 Å/s) onto thesubstrate. The resist film was lifted off in a 2-propanol (10% by vol.)HFE-7100 mixture to leave patterned pentacene on top of patternedPEDOT:PSS film.

The impact of fluorinated solvents on well-characterized andcommercially available organic electronic materials was tested. One suchorganic electronic material is poly-3-hexylthiophene (P3HT), aprototypical conjugated polymer which is soluble in common non-polarorganic solvents such as chlorobenzene and is extensively used inorganic thin film transistors (OTFTs). A nominally identical batch ofP3HT OTFTs was fabricated and tested them before and after a five minuteimmersion into a beaker filled with solvent and held at roomtemperature. In addition to the fluorinated solvents listed above,representative polar protic (isopropyl alcohol—IPA), polar aprotic(propylene glycol methyl ether acetate—PGMEA), and non-polar (p-xylene)solvents were also tested.

Another organic electronic material tested was ruthenium(II)tris(bipyridine) with hexafluorophosphate counter ions {[Ru(bpy)₃]²⁺(PF₆⁻)₂}. This material is an ionic metal complex which is soluble in polarsolvents such as acetonitrile and is used in electroluminescent devices.A nominally identical batch of [Ru(bpy)₃]²⁺(PF₆ ⁻)₂ electroluminescentdevices was fabricated, tested and exposed them to solvents according tothe protocol discussed above. The details of device structure andfabrication are given below.

The results of solvent treatment on device performance are shown in FIG.15 and are summarized Table 1 below:

TABLE 1 Non- Fluorous Protic Aprotic polar HFE HFE IPA PGMEA p-Xylene7100 7500 P3HT 95% 90%  0% 100% 100% [Ru(bpy)₃]²⁺ 45%  0% 85% 100% 100%(PF₆ ⁻)₂

For the P3HT transistors, the transfer characteristics before and aftersolvent immersion are shown in FIG. 15. The initial field-effect holemobility of the OTFTs was 1.0·10⁻³ cm² V⁻¹s⁻¹ with a device-to-devicevariation of 10%. As expected, the transistors fared reasonably well inIPA and PGMEA, showing only a minor decrease in performance. It shouldbe noted that PGMEA, which is extensively used in photolithography, hasbeen utilized in the photolithographic patterning of P3HT and a fewother organic materials. Immersion in the non-polar p-xylene, however,dissolved the P3HT film and resulted in severe device damage. On theother hand, immersion in the fluorinated solvents did not cause anydevice degradation, indicating that fluorinated solvents are excellentorthogonal solvents for P3HT.

Similar results were observed for the [Ru(bpy)₃]²⁺(PF₆ ⁻)₂electroluminescent devices. FIG. 15 shows the results of solventtreatment in the emission characteristics of the devices. The emissionshows the characteristic delay associated with the redistribution of thePF₆ ⁻ counter ions. Table 1 above shows the resulting loss in deviceexternal quantum efficiency upon solvent treatment. As expected,immersion in p-xylene resulted in a rather small loss of performance,while IPA caused a substantial decrease in device efficiency due to anincrease in device current, and PGMEA lead to shorting of the devicesand complete loss of electroluminescence. Once again, immersion influorinated solvents did not affect device performance. Therefore,fluorinated solvents are shown to be orthogonal solvents for at leasttwo organic materials with very different polarities: P3HT and[Ru(bpy)₃]²⁻(PF₆)₂.

To further demonstrate the orthogonality of fluorinated solvents, a[Ru(bpy)₃]²⁺(PF₆ ⁻)₂ electroluminescent device was operated in boilingHFE 7100 (61° C.) for one hour and no substantial change in itsperformance was observed. FIG. 15 shows the device operating in boilingHFE 7100. Similarly, immersion of a P3HT transistor in boiling HFE 7100for one hour did not change the transistor characteristics. In additionto the above mentioned device results, we performed optical and atomicforce microscopy on a variety of polymeric electronic materialsincluding polyfluorene, poly(9,9-didecylfluorene-co-benzothiadiazole)(F8BT) and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate)(PEDOT:PSS), before and after immersion in boiling HFE 7100. Nosignificant change of morphology and no pinhole formation, cracking, ordelamination was observed, confirming the orthogonality of fluorinatedsolvents even under extreme conditions.

In another example, using HFE 7100 and HFE 7500, the semiconductingpolymer poly(3-hexylthiophene) with head-to-tail regio-regularity >99%was obtained from Plextronics and used without further purification.Ru(bpy)₃]²⁺(PF₆ ⁻)₂ complex was synthesized according to knownreferenced procedures.

The electroluminescent devices were prepared as follows: 100 nm thickfilms were deposited on clean ITO/glass substrate by spin-coatingfiltered solutions of [Ru(bpy)₃]²⁺(PF₆)₂ (3 wt % in acetonitrle),followed by drying the films in nitrogen atmosphere at 60° C. for 12 h.After that 200 Å Au electrodes were directly deposited on the rutheniumcomplex film by thermal evaporation at a rate of 1 Å s⁻¹. The OTFTs wereprepared as follows: A P3HT solution (1% weight in1,2,4-trichlorobenzene) was spin coated at 3000 rpm on a highly-dopedsilicon wafer with a thermally-grown 200 nm SiO₂. The film was thenannealed at 100° C. for 1 h in nitrogen atmosphere. Source and drainelectrodes 300 Å Au electrodes were deposited onto the P3HT film via theshadow mask by thermal evaporation at a rate of 1 Å/s, defining channelsof that were 100 μm long and 1.8 mm wide.

This new dimension in solvent orthogonality which is enabled by the useof fluorinated solvents and supercritical CO₂ offers uniqueopportunities for the chemical processing of organic electronicmaterials. One example is in the area of photolithographic processing.Specifically, one can use a photoresist that is properly fluorinated tobe processable in fluorinated solvents Similar photoresists have beendeveloped for processing using supercritical CO₂. This approach to thepatterning of [Ru(bpy)₃]²⁺(PF₆ ⁻)₂ by employing a resist formulationcomposed of a resorcinarene photoresist and a photoacid generator (PAG)by a lift-off technique was successfully demonstrated as schematicallyillustrated in FIG. 16( a). The details of the photoresist synthesis andthe photolithographic patterning process are given elsewhere. In brief,an HFE-processable negative-tone photoresist by appending foursemi-perfluoroalkyl chains and eight acid-cleavable tert-butoxycarbonyl(t-Boc) groups to the resorcinarene molecule was synthesized. Thelithographic pattern of the photoresist is formed by turning it into aninsoluble form upon acid-catalyzed deprotection reaction, in which theacid is liberated from the photoacid generator (PAG) by UV exposure. Thedeveloped resist solubility in fluorinated solvents is restored via1,1,1,3,3,3-hexamethyldisilazane (HMDS) treatment at an elevatedtemperature. A positive image of the active material is created bydepositing an active material and subsequent resist lift off. Theprincipal scheme of the technique is depicted in FIG. 16( b). Apatterned [Ru(bpy)₃]²⁺(PF₆)₂ film with featured down to the 2 rtm scaleis shown in FIG. 16( c).

In conclusion, hydrofluoroethers (HFEs) represent a class of orthogonalsolvents that are benign to a wide variety of organic electronicmaterials. HFEs offer a unique opportunity to move beyond the usualpolar/non-polar axes in organic materials processing. Moreover, HFEs areenvironmentally friendly, “green” solvents, enabling chemical processingof organic electronic materials that can be readily adopted by industry.Coupled with fluorinated functional materials, they open new frontiersin materials processing, and have the potential to enable facilephotolithographic patterning for organic electronics.

Supercritical CO₂ as Solvent (FIG. 28)

According to another aspect of this disclosure, the supercritical CO₂may be used to pattern organic structures as well. Supercritical carbondioxide refers to carbon dioxide that is in a fluid state while alsobeing at or above both its critical temperature and pressure, yieldingspecific properties. Supercritical carbon dioxide is becoming animportant commercial and industrial solvent due to its role in chemicalextraction in addition to its low toxicity and environmental impact.Although supercritical carbon dioxide is widely used as an extractingsolvent in coffee decaffeinating, dry cleaning, fragrance extraction,etc., it is yet to be used as a solvent in the processing of organicelectronic and electrical structures. The use of supercritical carbondioxide is discussed below in connection with FIG. 29.

In one embodiment, supercritical CO₂ may be use with a fluorinatedphotoresist, such as the resorcinarene disclosed herein, to achieve arobust, high-resolution, high-throughput orthogonal process. Further,supercritical CO₂ may also be used with unfluorinated molecular glassphotoresists to create organic electronic or electrical structures.

In the case of a highly fluorinated photoresist material, for example,P(FDMA-TBMA), the photoresist material made patterns under UV exposureand development was carried out in supercritical carbon dioxideconditions. The developed photoresist image could be washed away in themixture of supercritical carbon dioxide (>95 part by vol.) andhexamethyldisilazane (<5 part by vol.) at 40° C., 2000-5000 psi. FIG. 29illustrates this concept.

While only certain embodiments have been set forth, alternatives andmodifications will be apparent from the above description to thoseskilled in the art. These and other alternatives are consideredequivalents and within the spirit and scope of this disclosure.

1. A method for patterning organic structures, the method comprising:coating a substrate with a layer of fluorinated photoresist material,wherein the substrate comprises a first thin film of a first activeorganic electronic material; selectively exposing portions of the layerof fluorinated photoresist material to radiation to form a first patternof exposed fluorinated photoresist material and a second pattern ofunexposed fluorinated photoresist material; removing the second patternof unexposed fluorinated photoresist material in a first fluorinatedsolvent thereby exposing portions of the substrate corresponding to thesecond pattern of unexposed fluorinated photoresist material; depositinga second thin film of a second active organic electronic material overthe first pattern of exposed fluorinated photoresist material and thesubstrate; and removing the first pattern of exposed fluorinatedphotoresist material with a second fluorinated solvent that is the sameas or different from the first fluorinated solvent, thereby removing thesecond thin film on the first pattern of exposed fluorinated photoresistmaterial and leaving a pattern of the second thin film on the portionsof the substrate corresponding to the second pattern of unexposedfluorinated photoresist material.
 2. The method of claim 1 wherein atleast one of the first and second active organic electronic materialcomprises a semiconducting polymer or a small molecule.
 3. The method ofclaim 1 wherein the first fluorinated solvent comprises ahydrofluoroether.
 4. The method of claim 1 wherein the secondfluorinated solvent comprises a hydrofluoroether.
 5. The method of claim1 wherein both the first and second fluorinated solvents comprise ahydrofluoroether.
 6. The method of claim 1 wherein the organic structureforms at least part of an organic thin film transistor, an organiclight-emitting diode, an organic photovoltaic, an organic sensor, or acombination thereof.
 7. The method of claim 1 wherein the layer offluorinated photoresist material is coated from a composition comprisinga fluorinated coating solvent.
 8. The method of claim 7 wherein thefluorinated coating solvent comprises at least one hydrofluoroether. 9.The method of claim 1 wherein the fluorinated photoresist materialcomprises a photo-acid generator.
 10. The method of claim 9 wherein thephoto-acid generator is non-ionic.